1. Field of the Invention
The present invention generally relates to articles of footwear, and more particularly, to a sole construction that may be incorporated into athletic footwear or as an insert into existing footwear and the like in order to store kinetic energy generated by a person. The sole construction has a combination of structural features enabling enhanced storage, retrieval and guidance of wearer muscle energy that complement and augment performance of participants in recreational and sports activities.
2. Description of the Related Art
From the earliest times when humans began wearing coverings on their feet, there has been an ever present desire to make such coverings more useful and more comfortable. Accordingly, a plethora of different types of footwear has been developed in order to meet specialized needs of a particular activity in which the wearer intends to participate. Likewise, there have been many developments to enhance the comfort level of both general and specialized footwear.
The human foot is unique in the animal kingdom. It possesses inherent qualities and abilities far beyond other animals. We can move bi-pedially across the roughest terrain. We can balance on one foot, we can sense the smallest small grain of sand in our shoes. In fact, we have more nerve endings in our feet than our hands.
We literally roll forward, rearward, laterally and medially across the bony structures of the foot. The key word is "roll." The muscles of the foot and ankle system provide a controlled acceleration of forces laterally to medially and vise-versa across the bony structure of the foot. In bio-mechanical terms these motions are referred to as pronation and supination. The foot is almost never applied flat, in relative position to the ground, yet shoe designers continue to anticipate this event.
The increasing popularity of athletic endeavors has been accompanied by an increasing number of shoe designs intended to meet the needs of the participants in the various sports. The proliferation of shoe designs has especially occurred for participants in athletic endeavors involving rigorous movements, such as walking, running, jumping and the like. In typical walking and running gaits, it is well understood that one foot contacts the support surface (such as the ground) in a "stance mode" while the other foot is moving through the air in a "swing mode." Furthermore, in the stance mode, the respective foot "on the ground" travels through three successive basic phases: heel strike, mid stance and toe off. At faster running paces, the heel strike phase is usually omitted since the person tends to elevate onto his/her toes.
Typical shoe designs fail to adequately address the needs of the participant's foot and ankle system during each of these successive stages. Typical shoe designs cause the participant's foot and ankle system to lose a significant proportion, by some estimates at least thirty percent, of its functional abilities including its abilities to absorb shock, load musculature and tendon systems, and to propel the runner's body forward.
This is because the soles of current walking and running shoe designs fail to address individually the muscles and tendons of a participant's foot. The failure to individually address these foot components inhibits the flexibility of the foot and ankle system, interferes with the timing necessary to optimally load the foot and ankle system, and interrupts the smooth and continuous transfer of energy from the heel to the toes of the foot during the three successive basic phases of the "on the ground" foot travel.
Moreover, in vigorous athletic activities, the athlete generates kinetic energy from the motion of running, jumping, etc. Traditional shoe designs have served merely to dampen the shock from these activities thereby dissipating that energy. Rather than losing the kinetic energy produced by the athlete, it is useful to store and retrieve that energy thereby enhancing athletic performance. Traditional shoe construction, however, has failed to address this need.
Historically, manufacturers of modem running shoes added foam to cushion a wearer's foot. Then, gradually manufacturers developed other alternatives to foam-based footwear for the reason that foam becomes permanently compressed with repeated use and thus ceases to perform the cushioning function. One of the largest running shoe manufacturers, Nike, Inc. of Beaverton, Oregon, has utilized bags of compressed gas as the means to cushion the wearer's foot. A German manufacturer, Puma AG, has proposed a foamless shoe in which polyurethane elastomer is the cushioning material. Another running shoe manufacturer, Reebok International of Stoughton, Mass., recently introduced a running shoe which has two layers of air cushioning. Running shoe designers heretofore have sought to strike a compromise between providing enough cushioning to protect the wearer's heel but not so much that the wearer's foot will wobble and get out of sync with the working of the knee. The Reebok shoe uses air that moves to various parts of the sole at specific times. For example, when the outside of the runner's heel touches ground, it lands on a cushion of air. As the runner's weight bears down, that air is pushed to the inside of the heel, which keeps the foot from rolling inward too much while another air-filled layer is forcing air toward the forefoot. When the runner's weight is on the forefoot, the air travels back to the heel.
In the last several years, there have been some attempts to construct athletic shoes that provide some rebound thereby returning energy to the athlete. Various air bladder systems have been employed to provide a "bounce" during use. In addition, there have been numerous advancements and materials used to construct the sole and the shoe in an effort to make them more "springy."
Furthermore, midsole and sole compression, historically speaking, can be very destabilizing. This is because pitching, tipping and lateral shear of the sole and midsole naturally rebound energies in the opposite direction required for control and energy transfers. Another perplexing problem for shoe engineers has been how to store energy as the foot and ankle system rolls laterally to medially. These rotational forces have been very difficult to absorb and control.
No past shoe designs, including the specific ones cited above, are believed to adequately address the aforementioned needs of the participant's foot and ankle system during walking and running activities in a manner that augments performance. The past approaches, being primarily concerned with cushioning the impact of the wearer's foot with the ground surface, fail to even recognize, let alone begin to address, the need to provide features in the shoe sole that will enhance the storage, retrieval and guidance of a wearer's muscle energy in a way that will complement and augment the wearer's performance during walking, running and jumping activities.
U.S. Pat. No. 5,595,003 to Snow discloses an athletic shoe with a force responsive sole. However, among the problems with the Snow embodiments is that they teach very thick soles comprised of tall cleats, a resilient membrane, deep apertures, and "guide plates." The combination of these components is undesirable because they make up a very heavy shoe. Furthermore, Snow shows numerous small parts that would be cost prohibitive to manufacture. These numerous small cleats cannot affect enough rubber molecules through the resilient membrane to provide a competitive efficiency gain without increasing the thickness of the membrane to the point of impracticability. The heavier and taller midsole and sole of Snow also position the foot further from the ground, providing less stability as well as less neuro-muscular input. Moreover, it takes a longer period of time for Snow's cleats to "cycle," i.e., penetrate and rebound. This produces a limiting effect for performance and efficiency gain potential.
Snow's cleats also require vertical guidance, i.e., anti-tipping, such as by Snow's required guide plate. Snow also fails to provide appropriate points of leverage for specific bone structures of the foot, control over the intrinsic rotational involvement of the foot and ankle system, bio-mechanical guidance, and the ability to produce tunable vertical vectors and transfer energy forward and rearward from heel, midfoot, forefoot and toes and vice-versa.
In my earlier invention disclosed in U.S. Pat. No. 5,647,145 issued Jul. 15, 1997, I teach an athletic footwear sole construction that enhances the performance of the shoe in several ways. First, the construction described in the '145 patent individually addresses the heel, toe, tarsal and metatarsal regions of the foot to allow more flexibility so that the various portions of the sole cooperate with respective portions of the foot. In addition, a resilient layer is provided in the sole which cooperates with cavities formed at various locations to help store energy.
While the advancements in shoe construction described above, including the '145 patent, have provided a great benefit to the athlete, there remains a continued need for increased performance of athletic footwear. There remains a need for an athletic footwear sole construction that can store an increased amount of kinetic energy and return that energy to the athlete to improve athlete performance.